The present invention relates generally to a shifting system for an outboard motor, and more particularly, to a shift interrupt system that facilitates the shifting of gears during the operation of the outboard motor.
Manual shift vehicles typically employ a clutch to facilitate shifting for engagement and disengagement of the gears in a standard shift transmission. However, in certain types of engine applications, such as marine outboard engines, there is no clutch system and gear shifting can occasionally demand more effort from an operator to shift from a positive gear position to a neutral position.
A typical outboard marine engine has three gearshift positions to provide operation, namely, forward, neutral, and reverse. Thus, the shifting of the gears from neutral to either the forward or reverse positions is accomplished by forcing the gears to mesh together while, on the other hand, the shifting from either forward or reverse gears into the neutral position is accomplished by forcing the gears to separate. In either instance, a mechanical linkage is used to carry out the forcing of the gears in one direction or the other.
While the shifting of the gears from a neutral positions into either the forward or reverse positions is normally fairly easy, it is sometimes very difficult to carry out the shifting of the gear from forward or reverse into neutral as a result of the loading that is on the gears due to the speed of the engine propelling the gears. Historically, there have been shift enabling interrupt systems that have been used to assist in the shifting from an in-gear position into a neutral position. In general, these known systems attempt to relieve the amount of force imposed upon the gears. When that force is excessive, one or more of the cylinders on the engine are caused to misfire. The resulting misfires consequently causes an uneven torque output which causes the load on the gears to drop to a lower amount momentarily. Thus, when the load on the gears is reduced, the mechanical linkage is allowed to cause the gears to move, and the engine is no longer forced to misfire.
One drawback, however, of the aforementioned system is that when the engine is caused to misfire, the engine speed is thereby reduced and is erratic. In situations where multiple, rapid shifts are initiated, such as in docking maneuvers, the reduction in the engine speed can be so severe that the engine can stall and require restart.
It is therefore desirable to design a shift enabling interrupt system for use with an outboard marine engine that allows for shifting of gears under increased engine load without engine misfire.